The Ancient Martian Shift

It takes a long time for things to change in the Universe. Time takes on an entirely different role when it comes to the lives of planets, stars, and galaxies. A million years in the life of a star or planet is the equivalent of a single day in the life of a human being. Human lifetimes come and go while stars and planets stay pretty much the same. However, just like human lives, where many days can build up to an important event, millions of years of lead-up can produce some incredible changes to a planet or star. New results published in Nature on March 2nd suggest that over 3 Billion years ago, Mars built up to a massive shift in it’s crust that changed the face of the planet forever.

Before this massive shift, Mars’ poles were in a different position, rivers could form from precipitation, and volcanic activity dominated one region in particular, known as the Tharsis plateau. 3.7 Billion years ago, the Tharsis region started to undergo a huge amount of volcanic activity that lasted hundreds of millions of years. This created a huge dome of rock that resulted in the elevated plateau we see today. This region includes some of the largest volcanoes in the Solar System, including the famous Olympus Mons. Once the region became large enough, it started to affect Mars’ rotation.

It’s like a pottery wheel. If the clay is spread symmetrically, it maintains it’s shape as it spins. But slap on a chunk of clay in one spot and the rotation causes the clay mass to wobble uncontrollably. With Mars, the Tharsis region became so massive that it caused the entire crust of Mars to shift with respect to it’s core. It’s like the peel of an orange detaching from the fruit inside and shifting independently.

A pottery wheel spins in equilibrium as long as the clay is balanced and symmetrical.

This shift brought the massive Tharsis plateau to the equator. Even though it restored equilibrium, it had other interesting effects that we are still seeing today. The outlines of the rivers that formed before the shift are still visible, and with the shifting crust, their origins and flow directions could be explained by climatologists. It also explains why underground reservoirs of water ice are located in the equatorial regions of Mars. Those regions would have originated near the former polar regions as expected, and then shifted along with the rest of the crust.

This is a huge result that has a lot of implications for future study of Mars and other Solar System worlds. As we learn more of Mars’ geologic, geographic, and climatological histories, this event will help to put them in context. It’s also possible this type of shift has happened on Earth in the past, though plate tectonics would have erased any trace of it long ago. Finally, if this type of shift did happen on other planets or Moons in our own solar system, we know how to identify it.

It just shows how much we still have to learn about the universe. Right when you think we have the solar system figure out, we get another curveball, another surprising result that changes our view of how everything formed. This is why I love astronomy, there is so much opportunity to discover new and unexpected results that have such an impact on our understanding of the universe.